This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2002-142699, filed (May 17), 2002; and No. 2002-173160, filed (June 13), 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an auto focusing system.
2. Description of the Related Art
A digital camera has an image pickup device which can electrically detect a video signal through a taking lens. In the digital camera, there is widely known a technology of carrying out focusing to bring it into correct focus by using luminance information of the video signal outputted from this image pickup device.
This is a technology of obtaining a lens position to improve image contract by fine-adjusting the taking lens. As it carries out control for a position of high contrast, the technology is generally called a sharpness detection auto focusing contrast system (AF).
On the other hand, in the single-lens reflex camera of a silver camera, an AF by a through the lens (TTL) phase difference system is generally employed. A luminous flux from an object which is captured through the taking lens is reflected on a movable mirror to be guided to an equivalent surface (primary image forming surface) of a film (primary image formation). Then, a secondary image is formed by a lens installed on the equivalent surface of the film, and the luminous flux is guided to an AF sensor to form a secondary image forming surface. The AF by the TTL phase difference system executes control so as to set a focusing position on the primary image forming surface by moving the lens on the primary image forming surface while executing ranging of a position of the secondary image forming surface.
In addition, the AF by the TTL phase difference system obtains a focusing position by separating the luminous flux of the secondary image forming optical system into two by using a separator lens (pupil division) to place them on a line sensor, and comparing deviation with a preset stipulated value.
Generally, in the camera, there have been presented a technology of a moving object prediction AF which focuses on a moving object, and a technology of carrying out vibration isolation by detecting blurring of a photographer.
For example, Jpn. Pat. Appln. KOKAI Publication No. 6-313920 presents a camera which obtains a characteristic amount of a light amount distribution obtained at a light receiving section, and detects blurring based on a change of the characteristic amount.
Jpn. Pat. Appln. KOKAI Publication No. 9-297335 presents a camera which comprises a moving object determination section for time-sequentially obtaining a plurality of focus detection signals by a focus detection section in accordance with a focusing state of an object image, carrying out prediction calculation for these focus detection signals, and carrying out focusing by a prediction operation to focus on the object moving in an optical axis direction of a taking lens, and a blurring prevention section for preventing the influence of blurring of a photographer, and which carries out no prediction operation when the blurring prevention section is operated.
The aforementioned contrast system AF is advantageous for miniaturizing a camera main body because the AF sensor can also be used for an image pickup sensor. However, since the taking lens is moved in a direction for improving image contrast to obtain a focusing position, it is impossible to detect the amount and the direction of focusing by sensing carried out once. Therefore, time for moving the taking lens is necessary, creating a problem of prolongation of so-called release time lag in a camera technology.
On the other hand, the TTL phase difference system AF can instantaneously obtain a focusing position as it only needs to obtain the focusing position based on deviation from the stipulated value. That is, a release time lag can be shortened. However, since the secondary image forming optical system is necessary to partially extract and pupil-divide the luminous flux from the object and to form an image again, there are problems that the number of components is increased to lead to a cost increase, and the camera main body itself is also enlarged.
Regarding the technology of the aforementioned publication, for example, while moving object detection is carried out by the technology disclosed in Jpn. Pat. Appln. KOKAI Publication No. 6-313920, a vibration isolation operation is inhibited. On the other hand, according to the technology disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-297335, if a mode is set to execute vibration isolation, the moving object prediction AF is not carried out.
These two technologies cannot coexist with each other simultaneously. It is because the moving object prediction AF technology which requires a small time lag to focus on the moving object conflicts with the vibration isolation technology which waits until the blurring of the photographer becomes small to permit exposure.
Therefore, vibration cannot be isolated during photographing of the moving image, conversely creating a problem of impossible photographing of the moving object if the vibration isolation mode is set. In photographs, there are many cases of photographing objects not moving or not moving so much, such as landscape photographs, snapshots while traveling or commemorative photographs, and it may be better that vibration can be isolated even at the slight sacrifice of focusing accuracy by the photographer.
According to these technologies, the moving object detection and the blurring detection are both made from changes in sensor data obtained by a plurality of timings. Furthermore, for the blurring detection, there has been known a technology which detects blurring based on an output of the AF sensor. That is, to carry out moving object detection, even if the AF sensor outputs are obtained by a plurality of timings, these are not used for hand shaking detection.
Thus, a feature of the present invention is an object to provide an auto focusing system capable of obtaining a focused focal point at a high speed. Another feature of the present invention is to provide an auto focusing system where a main body is not enlarged.
A further feature of the present invention is to provide a camera where moving object detection and hand shaking detection coexist, moving object prediction AF is carried out in a focusing detection area in which the moving object is detected and, in the other areas, hand shaking is detected to carry out moving object and hand shaking detections by using AF sensor outputs.
A first feature of the present invention is to provide an auto focusing system which comprises:
light receiving means for imaging an object as a digital image;
optical means for guiding a light from the object to the light receiving means;
a split image prism movable between a position immediately before a light receiving surface of the light receiving means in an optical path of the optical means and a position outside the optical path of the optical means; and
control means for detecting a deviation amount of a video signal based on light rays passed through the split image prism, and focusing the optical means based on the deviation amount.
A second feature of the present invention is to provide an auto focusing system which comprises:
light receiving means for imaging an object as a digital image;
optical means for guiding a light from the object to the light receiving means;
a split image prism installed in a position that is immediately before a light receiving surface of the light receiving means and is outside an optical path of the optical means;
deflection means which is removably inserted into the optical path of the optical means and guides a part of a luminous flux from the object to the split image prism; and
control means for detecting a deviation amount of a video signal based on light rays passed through the split image prism, and focusing the optical means based on the deviation amount.
A third feature of the present invention is to provide an auto focusing system comprising:
a light receiving section constituted of an imager such as a photoelectric transducer to image an object as a digital image;
an optical system which guides a light from the object to the light receiving section;
a split image prism movable between a position immediately before a light receiving surface of the light receiving section in an optical path of the optical system and a position outside the optical path of the optical system; and
a control section which detects a deviation amount of a video signal based on light rays passed through the split image prism, and focuses the optical system based on the deviation amount.
A fourth feature of the present invention is to provide an auto focusing system comprising:
a light receiving section constituted of an imager such as a photoelectric transducer to image an object as a digital image;
an optical system which guides a light from the object to the light receiving section;
a split image prism installed in a position that is immediately before a light receiving surface of the light receiving section and is outside an optical path of the optical system;
a deflection member which is removably inserted into the optical path of the optical system and guides a part of a luminous flux from the object to the split image prism; and
a control section which detects a deviation amount of a video signal based on light rays passed through the split image prism, and focuses the optical system based on the deviation amount.
A fifth feature of the present invention is to provide an auto focusing system which comprises:
focus detection means which is divided into a plurality of focus detection areas to output a focus detection signal;
image moving amount calculation means for calculating a moving amount of an object in each focus detection area based on the focus detection signal;
moving object determination means for determining movement of the object based on an output of the image moving amount calculation means; and
blurring amount calculation means for calculating an amount of blurring based on the focus detection signal regarding the focus detection area in which no movement of the object is determined by the moving object determination means.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.